plausible deniability

The guy in charge often wants to do things, and doesn't want the public to know that he ordered them done. So he has a private chat with a subordinate, the subordinate does the dirty, and then if things go wrong the subordinate can take the rap. As there is no record that his superior knew what was going on, he can thus deny involvement and be believed. Hence the name.

It works because the burden of proof is on those seeking to show that he was involved, and all he has to do is sow enough doubt.

plausible deniability works as a method to distance oneself from small-to-moderate scandals, but the larger the dirty deed, the harder it is to believe that the man at the top didn't know about it. For really large scandals, he is faced with the dilemma: admit involvement and take the penalty for that, or deny involvement and take the penalty for that, as he should have been involved.

Even while negotiating, they were secretly funding covert organisations that committed violence against us. I mentioned the recent revelations about million-rand payoffs to Inkatha that Mr De Klerk claimed not to know about. I stated that if a man in his position 'doesn't know about such things, then he is not fit to be head of the government'.

3: Oh, the agent misled you about our contract? We regret that. But those agents are independent third parties, who work on a comission basis and are not actually part of our company. I believe that the agent that you spoke to no longer works with us. However you did sign that contract.

The new CEO, John Sidgmore, pledges that he didn't know about the cooked books, although he was then a member of the company's board of directors. His defense: As a board member he just wasn't privy to the company's day-to-day operations.

Bernard Ebbers, WorldCom's founder and former CEO, who resigned in April amid questions about the more than $350 million in personal loans he received from the sinking company, says he didn't know about the misallocated funds either.

5:
The Iran-Contra scandal itself. I don't know much about it, but it seems that Oliver North and John Poindexter took the blame for President Ronald Reagan.
Consider Reagan's statements:
On 13 November 1986 Reagan denied arms deals: "We did not -- repeat, did not -- trade weapons or anything else for hostages, nor will we"
On 26 February 1987 "The Tower Commission report concludes that Reagan, confused and unaware, allowed himself to be misled by dishonest staff."
Then on 4 March 1987 he is forced to retract his denial: "A few months ago I told the American people I did not trade arms for hostages. My heart and my best intentions tell me that's true, but the facts and evidence tell me it is not. ... This runs counter to my own beliefs, to administration policy, and to the original strategy we had in mind."
Thanks to unperson, these and to this page

6:
In 2003, British Prime Minister Tony Blair did plausible deniability in reverse. He claimed that he didn't know that he didn't know. During the political fallout surrounding the claim made by his government prior to attacking Iraq that Saddam Hussein's forces had weapons of mass destruction ready to launch in 45 minutes, which was later shown to be false, and should not have been made as it was not supported by any reliable intelligence. He claimed to the Hutton enquiry that he had no knowledge that the claim was trumped-up, and thus it is plausible that he could affirm it without knowingly telling a lie.